NAME

       fixsub  -  Safe  function to subtract fixed point numbers clamping underflow. Allegro game
       programming library.

SYNOPSIS

       #include <allegro.h>

       fixed fixsub(fixed x, fixed y);

DESCRIPTION

       Although fixed point numbers can be subtracted with the normal '-' integer operator,  that
       doesn't  provide any protection against overflow. If overflow is a problem, you should use
       this function instead. It is slower than using  integer  operators,  but  if  an  overflow
       occurs  it  will  set  `errno'  and  clamp  the  result, rather than just letting it wrap.
       Example:

          fixed result;
          /* This will put 4965 into `result'. */
          result = fixsub(itofix(5000), itofix(35));
          /* Sets `errno' and puts -32768 into `result'. */
          result = fixsub(itofix(-31000), itofix(3000));
          ASSERT(!errno); /* This will fail. */

RETURN VALUE

       Returns the clamped result of subtracting `y' from `x', setting `errno' to ERANGE if there
       was an overflow.

SEE ALSO

       fixadd(3alleg4), fixmul(3alleg4), fixdiv(3alleg4)